Support apparatus, system and method

ABSTRACT

A therapeutic support device includes a bladder having one or more independently inflatable compartments, each including a plurality of inflatable cells. When inflated, each inflatable cell forms a contact node that may support a user or another object disposed thereon. The inflatable compartments can be alternately inflated and deflated such that contact pressure can be applied to and relieved from corresponding portions of the user&#39;s body in an alternating manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationSer. No. 61/390,016, filed Oct. 5, 2010, and U.S. ProvisionalApplication Ser. No. 61/535,294, filed Sep. 15, 2011, the disclosures ofwhich are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. The Technical Field

The present invention is directed to a therapeutic support apparatus,system and method that may be used for mitigating the formation ofand/or assisting in the treatment of decubitus ulcers (also sometimesreferred to as “pressure ulcers”).

2. The Prior Art

Decubitus ulcers can result from excessive and unrelieved pressureapplied to a person's body. For example, decubitus ulcers can resultfrom a person lying on a bed, mattress, pad or other support surface inone position for an extended period of time, during which the interfacepressure between the support surface and the user's body exceeds thevascular occlusion threshold. The vascular occlusion threshold is themaximum pressure that may be applied to a person's skin by a supportingsurface without cutting off subcutaneous or capillary blood flow in thearea of the person's body in contact with the supporting surface. Putanother way, subcutaneous blood flow is likely to be cut off in areas ofcontact between a user and a supporting surface if the pressure appliedto the person by the support surface exceeds the vascular occlusionthreshold. The vascular occlusion threshold is generally deemed to beabout 28-32 mm Hg (about 0.5 psi) but can be lower, particularly inusers having low blood pressure.

Excessive and unrelieved heat and moisture about the skin and shearforces applied to the skin also can contribute to the formation ofdecubitus ulcers. Such shear forces can pinch off blood vessels,particularly perforator vessels perpendicular to the skin, and,therefore, inhibit subcutaneous blood flow.

Traditional methods and apparatus for mitigating the formation of andassisting in the treatment of decubitus ulcers involve distributing theuser's weight over a relatively large area (typically as large an areaas possible) of a support surface so that the interface pressure betweenthe user's body and the support surface generally remains below thevascular occlusion threshold (such techniques sometimes are referred toas “redistribution”). Such methods may further involve alternating areasof the support surface over which the user's weight is distributed.

For example, redistribution techniques sometimes involve the use ofrelatively thick air mattresses having two alternately inflatablecompartments that are operated at low internal pressures (typically0.5-1.0 psi or less). Operation at such low pressures allows the user'sbody weight to be distributed over a relatively large area such that arelatively low interface pressure may be realized. One approach uses anair mattress having two alternately inflatable compartments, eachdefining a plurality of relatively large, generally circular air cellsoperated at pressures of about 25 mm Hg (about 0.5 psi) that distributethe user's weight over a relatively large surface area. The air cellsare about 5 inches in diameter, and the air mattress has a thickness ofabout 2.5 inches or greater when inflated. Another approach involves asupport pad having smaller, more-closely spaced, and elongated aircells. The air cells and fluid channels connecting them are formed intothe surface of the pad.

Redistribution techniques have not proven to be entirely satisfactory.Such techniques do not necessarily provide for maintenance of adequatesubcutaneous blood flow or adequate relief from shear and environmentaleffects.

SUMMARY OF THE DISCLOSURE

This disclosure describes exemplary support surface overlays and otherapparatus, systems, and methods for supporting a patient or other userand controlling the microclimate about the user in a manner that maymitigate the formation and/or assist in the treatment of pressureulcers. The support surface overlays depart significantly from supportapparatus using redistribution techniques in that they selectivelyimpart relatively high interface pressure to relatively small areas of auser's body. Indeed, the support surface overlays may selectively impartupon the user interface pressures substantially exceeding the vascularocclusion pressure at certain points of contact between the apparatusand the user. At the same time, however, the support surface overlaysmay impart interface pressures substantially lower than the vascularocclusion pressure (or no interface pressure at all) at other areas ofthe user's body, for example, areas adjacent to such points of contactor areas corresponding to interstices between such points of contact. Assuch, subcutaneous blood flow about such points of contact (sometimesreferred to herein as “interstitial blood flow”) may actually beimproved over support apparatus involving generally lower interfacepressures at the points of contact. Also, the contact points may closelymatch the relative spacing of the skin's perpendicular perforatorvessels and thereby may be less likely to pinch off those vessels as aresult of skin shear as compared to apparatus having larger cell sizesand/or spacing, which can involve substantial skin shear due toenvelopment or hammock effects, as would be understood by one skilled inthe art.

An illustrative support surface overlay takes the form of a bladderhaving one or more inflatable compartments. Each inflatable compartmentdefines one or more relatively small inflatable cells. The inflatablecells of a given compartment and/or the support surface overlay as awhole may be arranged in a matrix of rows and columns or in anothergeometric form, for example, concentric circles or interwoven spirals.When an inflatable compartment is inflated with a fluid (for example,air, another gas or a liquid), at least some of the inflatable cellsalso become inflated so as to form contact nodes that impart focusedpressure at discrete points on a user's body. These contact nodes alsodefine interstices there between, at least some of which interstices mayprovide the user's body with partial or complete relief from contactpressure. Such interstices also may form channels allowing for flow ofair or another fluid there through. Such fluid flow can be used tocontrol or condition the temperature and/or humidity at the interfacebetween the support surface overlay and a user disposed thereon.

In embodiments including more than one inflatable compartment, theindividual inflatable compartments can be independently inflated. Also,the inflatable cells of each inflatable compartment may be locatedadjacent or between the inflatable cells of one or more other inflatablecompartments. In such embodiment, the inflatable cells and intersticesmay be arranged in rows or in other manners, for example, in sinuousshapes.

Nipple-like protrusions can be provided in connection with one or moreof the inflatable cells. Where provided, the nipple-like protrusions canfurther focus pressure at discrete points on a user's body. Thenipple-like protrusions can be formed into the support surface overlayso that they are inflated with their respective inflatable cells or theycan be joined to the support surface overlay as a sealed bubble filledwith air, another fluid, a gel, or a solid material. They also could beformed of a solid material attached to the support surface overlay orintegrally formed with the support surface overlay. Alternatively, theycan be provided in a flexible overlay sheet formed separately from andplaced over or fixed to the support surface overlay.

In operation, a user can sit or lie on the support surface overlay, andthe fluid pressure in the one or more inflatable compartments can beadjusted so that the inflatable cells form corresponding contact nodesand interstices there between. The contact nodes may focus pressure atcertain points or portions of the user's body, while the interstices mayallow for relief of pressure from other points or portions of the user'sbody. The internal inflatable compartment pressure that might berequired to achieve the desired effect may be a function of the size ofthe inflatable cells, the number of inflatable cells in contact with auser, the spacing of the inflatable cells from each other, and theweight of the user. Other factors may be relevant, as well. The internalinflatable compartment pressure might range from 2 psi or less to 15 psior more depending on the application and the design and dimensions ofthe support surface overlay and elements thereof.

Also, the pressure in the inflatable compartment(s) can be varied in oneor more patterns in a manner that massages the user and further promoteslocalized capillary and lymphatic blood flow. For example, in a supportsurface overlay having only one inflatable compartment, the inflatablecompartment could be sequentially inflated and deflated. In a supportsurface overlay having two inflatable compartments, both compartmentscould be simultaneously inflated or deflated, or the two compartmentscould be inflated and deflated in an alternating manner, so that therespective contact nodes of the two compartments alternately support theuser's body at different locations, thereby changing the locations ofthe user's body where subcutaneous blood flow might be inhibited due tocontact with the contact nodes.

The level of control of pressure relief and massaging could be increasedby increasing the number of inflatable compartments used in a particularsupport surface overlay and/or increasing the number of support surfaceoverlays used in a particular application and/or by modifying the mannerin which the control mechanisms inflate and deflate the compartments.

The support surface overlay may be used in place of a mattress, pillowor pad. Alternatively, it may be used on top of a mattress, pillow, pador any other pressure redistribution surface. It may also be used uponor otherwise in connection with chairs, vehicle seats, wheelchairs, andother support surfaces upon which a patient might be disposed for longperiods of time.

The support surface overlay also can be placed on an operating table orimaging device, for example, an x-ray machine, fluoroscope, CT scanner,MRI apparatus, etc., to provide pressure relief to a user lying thereon.Preferably, the bladder (and nipple-like protrusions, if provided)appear transparent to such imaging devices.

The support surface overlay can be included as part of a systemincluding control mechanisms, auxiliary support devices, underlyingsupport surfaces, and/or other elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings are part of the specification and illustratecertain exemplary embodiments of the present invention as well as theircomponent parts. The components in the drawings are not necessarily toscale, emphasis instead being placed upon illustrating the principles ofthe present invention.

FIG. 1 is a top plan view of an exemplary support surface overlayaccording to the present invention;

FIG. 2 is a section view of an inflatable region of the support surfaceoverlay of FIG. 1;

FIG. 3 is a top plan view of the support surface overlay of FIG. 1 withnipple-like protrusions provided thereon;

FIGS. 4A and 4B are section views of an inflatable region of differentembodiments of the support surface overlay of FIG. 3;

FIG. 5 is an isometric view of a flexible overlay sheet according to anon-limiting embodiment of the present invention;

FIG. 6 is a plan view of a support surface overlay having relief cutsformed therein;

FIG. 7 is a perspective view of an articulating support surface overlay;

FIGS. 8 and 9 are representations of a test fixture;

FIG. 10 is a flow chart illustrating a test procedure;

FIG. 11 illustrates contact patterns obtained from tests of an exemplarysupport surface overlay;

FIG. 12A is a plot of contact area vs. inflation pressure for anexemplary support surface overlay;

FIG. 12B is a plot of linear non-contact vs. inflation pressure for anexemplary support surface overlay;

FIG. 13 is a schematic representation of an exemplary system foroperating an exemplary support surface overlay;

FIG. 14 is a layout drawing of an exemplary control panel for use withthe system shown in FIG. 13;

FIG. 15 is a block representation of various operating modes of anexemplary system for operating an exemplary support surface overlay;

FIG. 16 is a graphic representation of an exemplary start cycle mode foran exemplary system for operating an exemplary support surface overlay;

FIG. 17 is a graphic representation of an exemplary end cycle mode foran exemplary system for operating an exemplary support surface overlay;

FIG. 18 is a graphic representation of an exemplary safety stop cyclemode for an exemplary system for operating an exemplary support surfaceoverlay;

FIGS. 19-21 are graphic representations of several predefined patternsand cycles of inflation/deflation of an exemplary system for operatingan exemplary support surface overlay;

FIG. 22 is a perspective view of an exemplary liner bag for use inconnection with an exemplary support surface overlay;

FIGS. 23A and 23B are plan and section views of an exemplary padincluding an exemplary support surface overlay;

FIG. 24 is a perspective view of an exemplary liner bag and foam insertin combination with an exemplary support surface overlay;

FIG. 25A is a top plan view of a support surface overlay including meansfor providing climate control proximate an upper side thereof;

FIG. 25B is a partial section view of the support surface overlay ofFIG. 25A;

FIG. 25C is another partial section view of the support surface overlayof FIG. 25A;

FIG. 25D is a top plan view of a portion of the support surface overlayof FIG. 25A;

FIG. 25E is an exploded perspective view of the support surface overlayof FIG. 25A;

FIG. 26A is a perspective view of a support surface overlay includingattachment straps;

FIG. 26B is a top plan view of a support surface overlay includingattachment straps and hand holds;

FIG. 27A is a top plan view of a support surface overlay disposed withina housing also containing a lubricating fluid;

FIG. 27B is a section view of the support surface overlay of FIG. 27A;

FIG. 28 is a cross-sectional side elevation view of a portion of aprosthetic device including a support surface overlay;

FIG. 29 is a cross-sectional side elevation view of a portion of aprosthetic device for use with support surface overlay of FIG. 28;

FIG. 30 is a cross-sectional side elevation view of a portion of anotherprosthetic device for use with support surface overlay of FIG. 28;

FIG. 31 is a graph showing how the thickness of a support surfaceoverlay may vary with varying pressure; and

FIG. 32 is a representation of test data as may be obtained using aparticular test methodology.

DETAILED DESCRIPTION OF THE DRAWINGS

The drawings illustrate exemplary embodiments of support surfaceoverlays, control systems for operating the support surface overlays,and other elements that may be incorporated into or otherwise used withthe support surface overlays.

1. SUPPORT SURFACE OVERLAYS

FIGS. 1 and 2 illustrate a support surface overlay 100 in the form of abladder formed from a first sheet 102 (sometimes referred to herein as“upper” sheet 102) and a second sheet 104 (sometimes referred to hereinas “lower” sheet 104) of flexible material. (References to “upper” and“lower” and to directions and orientations herein generally are for thepurpose of illustration and should not be deemed to limit the manner inwhich devices or components discussed herein may be oriented.) Uppersheet 102 and lower sheet 104 may be substantially flat or planar orotherwise form a substantially continuous surface, at least at pointswhere upper sheet 102 and lower sheet 104 are joined to each other.(Upper sheet 102 and/or lower sheet 104 may include discontinuities orformed elements at points away from such junctions, as discussed furtherbelow.) Upper sheet 102 and lower sheet 104 may be made of any suitablematerial, as would be recognized by one skilled in the art. Preferably,but not necessarily, such material resists taking on electrical chargeso as to not become a potential source of electrostatic discharge. Inone embodiment, upper sheet 102 and lower sheet 104 may be made of Dow(or Lubrizol) Pellethane 2103-90AE having a nominal thickness of about0.014 in.

Upper sheet 102 is fused to lower sheet 104 at predetermined locationsusing an RF welding technique or any other technique suitable forjoining upper sheet 102 to lower sheet 104 in a generally fluid-tightmanner, thereby forming one or more seams 106. Each seam 106 may includea single fusion or weld line or two or more spaced-apart fusion or weldlines. In embodiments where a seam 106 includes multiple fusion or weldlines, such fusion or weld lines preferably are arranged such that theygenerally conform to each other. Support surface overlay 100 may besubstantially flat or planar when deflated. Preferably, upper and lowersheets 102, 104 and seams 106 appear transparent to a medical imagingdevice.

Seams 106 divide support surface overlay 100 into first and secondindependent and separately inflatable compartments 108 and 110. In theFIG. 1 embodiment, first inflatable compartment 108 includes a firstcompartment manifold 112 and a number of first compartment rows 114extending therefrom. Similarly, second inflatable compartment 110includes a second compartment manifold 116 and a number of secondcompartment rows 118 extending therefrom. First compartment rows 114 areshown as generally adjacent and interspersed with second compartmentrows 118. In other embodiments, first and second inflatable compartments108, 110 can be arranged in other ways.

Adjacent first compartment rows 114 and second compartment rows 118 areshown as sharing a common seam 106 having a single fusion or weld line.This design allows for efficient manufacturing because a single RF weldcan be used to form inflatable multiple compartments. It also allows fora relatively high density of first and second compartment rows 114, 118in a given footprint. In other embodiments, first inflatable compartment108 and second inflatable compartment 110 need not share a common seam106. In further embodiments, second inflatable compartment 110 can beomitted. In such embodiments, seams 106 could simply define the boundarybetween first inflatable compartment 108 and other portions of supportsurface overlay 100.

In FIG. 1, first compartment 108 is shown as including four firstcompartment rows 114, and second compartment 110 is shown as includingfour second compartment rows 118. In other embodiments, either or bothof first compartment 108 and second compartment 110 could include asmany or as few (as few as one) rows 114, 118 as may be practical. Firstcompartment manifold 112 and second compartment manifold 116 are shownas being aligned with the sides of support surface overlay 100, andfirst compartment rows 114 and second compartment rows 118 are shown asbeing aligned with the sides of support surface overlay 100 and orientedat right angles to manifolds 112 and 116, respectively. Manifolds 112,116 and rows 114, 118 could be oriented in other manners, as well.

In FIG. 1, support surface overlay 100 is shown as having a generallysquare overall shape. In other embodiments, support surface overlay 100could have other rectangular, non-rectangular or curvilinear overallshapes. For example, support surface overlay 100 could have a generallyelongated shape. In such an embodiment, rows 114, 118 could extend in adirection corresponding to the longer (length) or shorter (width)dimension of support surface overlay 100. In another embodiment, supportsurface overlay 100 could have a circular shape. In such an embodiment,first and second compartments 108, 110 could be arranged, for example,in concentric circles, spirals, or in another two-dimension orthree-dimensional manner, rather than in rows. In such embodiments,manifolds 112, 116 could be omitted.

Seams 106 are shaped to define a number of inflatable cells 120 in fluidcommunication with each other in each of first compartment rows 114 andsecond compartment rows 118, for example, as shown in FIG. 1. Wheninflated, inflatable cells 120 form corresponding contact nodes 122 anddefine interstices between neighboring contact nodes, as shown, forexample, in FIG. 2 and as discussed further below. Seams 106 are shownas being sinusoidal or generally sinuous in shape, such that inflatablecells 120 have a generally circular shape. As such, when inflated,inflatable cells 120 take on a generally spherical shape, therebyforming contact nodes 122, as shown in FIG. 2. The portion of inflatablecompartments 108 and 110 joining adjacent inflatable cells 120 maypreclude inflatable cells 120 and contact nodes 122 from becomingperfectly spherical, as would be recognized by one skilled in the art.Indeed, in the FIG. 1 embodiment, the shape of contact nodes 122 may begenerally football-like at relatively low inflation pressures and becomemore spherical at increased inflation pressures.

In other embodiments, seams 106 could have other repeating ornon-repeating shapes, yielding inflatable cells 120 having correspondingshapes. For example, seams 106 could be shaped in the form of: repeatingramped waves that, for example, ramp up, level off, ramp down and leveloff, so as to form inflatable cells 120 having a generally hexagonalshape; repeating square waves forming inflatable cells 120 having agenerally square shape; repeating saw tooth shapes forming inflatablecells 120 having a generally diamond-like shape; or repeating saw toothshapes alternating with generally linear shapes thereby forminginflatable cells 120 having a generally triangular shape. In suchembodiments, contact nodes 122 take on corresponding shapes wheninflatable compartments 108, 110 (including inflatable cells 120) areinflated.

A first fluid conduit 124 can be provided in fluid communication withthe interior region of first compartment 108 and a second fluid conduit126 can be provided in fluid communication with the interior region ofsecond compartment 110 so that the compartments can be selectivelycharged with and emptied of a fluid (for example, air or another gas ora liquid). Fluid conduits 124, 126 can be made of a plastic material oranother suitable material. The ends of fluid conduits 124, 126 attachedto support surface overlay 100 can be disposed between upper and lowersheets 102, 104. Alternatively, the ends of fluid conduits 124, 126attached to support surface overlay 100 could be disposed throughcorresponding perforations in either of upper and lower sheets 102, 104.In either event, such ends could be RF welded or otherwise attached toupper and/or lower sheet 102, 104 in a manner allowing for asubstantially fluid tight connection there between.

In some embodiments, support surface overlay 100 may be provided withnipple-like protrusions 128 at one or more inflatable cells 120. FIG. 3illustrates one such embodiment as viewed from above. As illustrated inFIG. 4A, nipple-like protrusions 128 can be formed as part of uppersheet 102 of support surface overlay 100 and inflated along with theassociated inflatable cells 120 when the corresponding inflatablecompartment 108, 110 is inflated. Alternatively, as illustrated in FIG.4B, nipple-like protrusions 128 can be provided as a third layer 130attached to upper sheet 102 of support surface overlay 100 by RF weldingor another suitable technique. In such embodiments, air, another fluid,a gel, or a solid material could be captured between upper sheet 102 ofsupport surface overlay 100 and third layer 130 so that nipple-likeprotrusions 128 maintain their shape even when the correspondinginflatable compartment 108, 110 of support surface overlay 100 isdeflated. As another alternative, third layer 130 could be embodied as asolid piece of material attached to upper sheet 102 in a suitablemanner. Preferably, nipple-like protrusions 128 and their constituentcomponents appear transparent to a medical imaging device.

Nipple-like protrusions 128 need not be integral with upper sheet 102 ofsupport surface overlay 100, as discussed above. Instead, as illustratedin FIG. 5, nipple-like protrusions 128 may be provided on a separate,flexible overlay sheet 132 that can be disposed on support surfaceoverlay 100 so that nipple-like protrusions 128 are aligned overinflatable cells 120 of first and/or second inflatable compartments 108and 110. In such embodiments, nipple-like protrusions 128 can be formedby fusing two layers of material and capturing air, another fluid or agel therebetween in the desired protruding shape in a manner similar tothat discussed above in connection with embodiments wherein nipple-likeprotrusions 128 are integral with upper sheet 102 of support surfaceoverlay 100. Alternatively, nipple-like protrusions 128 and overlaysheet 132 could be integrally formed as a single sheet of material, suchas plastic or rubber. Preferably, nipple-like protrusions 128 andoverlay sheet 132 are substantially transparent to medical imagingdevices. In use, overlay sheet 132 may simply be placed over supportsurface overlay 100, or overlay sheet 132 may be permanently attached toupper sheet 102 of support surface overlay 100 using RF welding,bonding, or another suitable attachment mechanism.

With reference to FIGS. 1, 26A and 26B, support surface overlay 100 mayinclude one or more straps 134 for attaching support surface overlay 100to an underlying support surface, for example, a bed or seat. Straps 134could be made of any suitable material and attached to support surfaceoverlay 100 in any suitable manner. For example, straps 134 or relevantportions thereof could be made of a material compatible with thematerial of which support surface overlay 100 is made so that straps 134could be RF welded to support surface overlay 100. Alternatively,support surface overlay 100 could include slots 158 (as shown in FIG.26B), grommets and/or other apertures (not shown) proximate theperimeter thereof through which straps 134 could be threaded.

Only two straps 134 are illustrated in FIG. 1, extending from corners ofsupport surface overlay 100. In practice, support surface overlay couldinclude more straps 134, as desired, and straps 134 could extend fromany portion of support surface overlay 100 including other corners orsides thereof. For example, as shown in FIGS. 26A and 26B, straps 134could extend from the sides and/or ends of support surface overlay 100.As shown in FIGS. 26A and 26B, straps 134 could be attached to supportsurface overlay 100 at both ends and configured to hook over the cornerof a mattress 90 to secure support surface overlay 100 to the mattress.In such embodiments, at least portions of straps 134 could be made of anelastic material. In other embodiments, straps 134 could include bucklesor hook-and-loop fasteners 135 or other adjusting and securing means sothat straps 134 can be used to secure support surface overlay 100 to anunderlying support surface, for example, mattress 90 or another supportsurface.

With reference to FIG. 26B, support surface overlay 100 may include handholds 156 cut into support surface overlay 100 about the peripherythereof, thereby providing means for personnel to securely grip andcarry support surface overlay 100 with a user disposed thereon.

The overall length and width of support surface overlay 100 can beselected as desired for a particular application. For example, supportsurface overlay 100 can be sized to overlie a standard mattress,individual sections of an articulating mattress as might be used in anarticulating hospital bed, a catheter table, an MRI table, an operatingtable, a wheelchair seat, a vehicle seat, another form of seat, thelimb-receiving cup of a prosthetic device, another form of supportsurface for an individual, etc.

As shown in FIG. 7, support surface overlays 100 can include multiplebladder sections, each including separate and distinct first and/orsecond inflatable compartments 108, 110, can be formed from a singleupper sheet 102 and lower sheet 104. Such embodiments enablearticulation of upper sheet 102 and lower sheet 104 withoutpneumatically or hydraulically pinching portions of inflatablecompartments within ones of such bladder sections.

Preferably, but not necessarily, support surface overlay 100 issufficiently flexible so that it may be rolled up for shipping orstorage and so that it is “self contouring” to an underlying supportsurface it might be placed upon, for example, a pressure redistributionsurface or any other flat, concave, convex or otherwise contouredsurface.

In operation, first inflatable compartment 108 and second inflatablecompartment 110 can be selectively and independently inflated anddeflated. When either of inflatable compartments 108, 110 is inflated,the inflatable cells 120 of the respective compartment inflate to agenerally spherical shape (for example, a compressed spherical shapesuch as that shown in FIG. 2) and form contact nodes 122 as discussedabove. Contact nodes 122 can support a load, for example, a human body.The inflation pressure within inflatable compartments 108, 110 can beselected such that a body supported by support surface overlay 100 restssubstantially upon contact nodes 122 and preferably not upon other partsof support surface overlay 100, for example, the interstices betweenneighboring contact nodes 122. In practice such inflation pressures mayrange from 1 psi or less to 15 psi or more, depending on theconfiguration of support surface overlay 100. In this state, theinterface pressure between contact nodes 122 and the body supportedthereon may substantially exceed the vascular occlusion threshold suchthat subcutaneous blood flow in areas of the body impinging contactnodes 122 may be substantially inhibited or even cut off. At the sametime, however, the interface pressure between other portions of supportsurface overlay 100, for example, the interstices between neighboringcontact nodes 122, and the body supported by contact nodes 122 may besubstantially less than the vascular occlusion threshold, such thatsubcutaneous blood flow in areas of the body overlying the intersticesmay be preserved or otherwise not substantially inhibited. Indeed, inthis state, there may be substantially no contact between the bodysupported by contact nodes 122 and the interstices between neighboringcontact nodes 122, such that the interface pressure in theseinterstitial regions may be as little as substantially zero. To theextent that there is no contact in the foregoing regions, air or anotherfluid may be channeled through such regions to, for example, controlheat and humidity in such regions, as will be discussed further below.

In operation, first and second inflatable compartments 108, 110 could bealternately inflated and deflated according to one or more predeterminedpatterns or cycles such that particular contact nodes 122 generally donot impart pressure greater than the vascular occlusion threshold uponthe same portions of a body lying on support surface overlay 100 forlonger than a predetermined, uninterrupted period of time. For example,first inflatable compartment 108 could be inflated and second inflatablecompartment 110 could be deflated for a first predetermined period oftime, during which time a first set of contact nodes 122 correspondingto the inflatable cells 102 of first inflatable compartment 108generally would impart substantial pressure (that might exceed thevascular occlusion threshold) upon corresponding first portions of abody lying on support surface overlay 100. Upon expiration of theforegoing predetermined period of time, second inflatable compartment110 could become inflated and first inflatable compartment 108 couldbecome deflated for another predetermined period of time, during whichtime a second set of contact nodes 122 corresponding to the inflatablecells 102 of second inflatable compartment 110 generally would impartsubstantial pressure (that might exceed the vascular occlusionthreshold) upon corresponding second portions of a body lying on supportsurface overlay 100. The second portions of the body typically would besubstantially different from the first portions of the body.

The foregoing cycle could be repeated indefinitely. In some modes ofoperation, first inflatable compartment 108 could become completelydeflated before any substantial inflation of second inflatablecompartment 110 and vice versa. In other modes of operation, firstinflatable compartment 108 could become deflated while second inflatablecompartment 110 becomes inflated and vice versa. In further modes ofoperation, second inflatable compartment 110 could become completelyinflated before first inflatable compartment 108 begins to deflate andvice versa.

In addition to controlling subcutaneous blood flow, operation of supportsurface overlay 100 as discussed above also can provide massaging actionto a user lying thereon. For example, alternately inflating anddeflating first and second inflatable compartments 108, 110 can yield anoscillating, wave-like pattern of movement across the inflatablecompartments 108, 110 of one or more support surface overlays 100 a usermight be disposed upon to massage one or more areas of a user's body andto encourage interstitial blood flow.

The drawings generally illustrate a support surface overlay 100 havingtwo inflatable compartments 108, 110. In other embodiments, a supportsurface overlay 100 could include more than two inflatable compartments108, 110 to enable increased complexity of the patterns of movement ofinflatable cells 120 that can be created by inflating and deflating theindividual inflatable compartments of support surface overlay 100.Indeed, each inflatable cell 120 of support surface overlay 100 could beembodied as a separate and distinct inflatable compartment. In furtherembodiments, a support surface overlay 100 could include a singleinflatable compartment. In some embodiments, support surface overlay 100could include one or more permanently filled inflatable compartmentssimilar to one or more of the inflatable compartments described herein.In such embodiments, the permanently filled compartments preferablywould be filled with a fluid, for example, a silicone hydraulic fluid,that would not permeate upper and lower sheets 102, 104.

A support surface overlay 100 dimensioned so that it satisfies one ormore of Criteria A-D set forth below may provide for the foregoingsupport characteristics (sometimes referred to herein as “Dabireffects”), that is, relatively high local interface pressure betweencontact nodes 122 and portions of a user's body supported thereon, andrelatively low or no interface pressure between interstices defined bycontact nodes 122 and a user supported thereon. With reference to FIG.2, relevant dimensions may include the maximum thickness “t” of any ofinflatable cells 120 of support surface overlay 100 when inflated andfree of any substantial external load. With reference to FIG. 1,relevant dimensions may also include the nominal diameter “d” ofinflatable cells 120 (or other relevant dimension where inflatable cells120 are not generally circular), the spacing “h” between neighboringinflatable cells 120 within a given inflatable row 114, 118 of first orsecond inflatable compartment 108, 110 (sometimes referred to herein as“horizontal spacing” or “horizontal pitch”), and the spacing “v” betweeninflatable cells 102 within a given “column” of inflatable rows 114, 118(sometimes referred to herein as “vertical spacing” or “verticalpitch”). (As used in this context, the terms “horizontal” and “vertical”refer to orientation relative to rows of inflatable cells 120 as setforth above.) In embodiments wherein inflatable cells 120 are notarranged in columns substantially normal to the rows, the spacing “v”could be measured from a first contact node located in a first row to asecond contact node located in a second row that is nearest a linenormal to the first row and passing through the first contact node. Thespacing between inflatable cells 120 typically is measured from centroidto centroid of the corresponding contact nodes, with inflatable cells120 inflated, unless otherwise noted. A support surface overlay 100 notsatisfying any of Criteria A-D might nevertheless provide Dabir effects,and other criteria may exist which may define whether a support surfaceoverlay 100 is likely to provide Dabir effects.

Criterion A—Bladder Thickness

A support surface overlay 100 with inflatable cells 120 having a maximumnominal thickness t, when fully inflated and free of external loads, ofno more than about 2.0 inches may provide the Dabir effect. As used inthis context, the term “fully inflated” means inflated to a pressureinsufficient to cause plastic deformation of inflatable cells 120 orsupport surface overlay 100 generally and beyond which an increase inpressure results in at most an insignificant increase in thickness ofinflatable cells 120, for example, as illustrated in FIG. 31. Supportsurface overlay 100 thickness t can be measured using any suitablemeans, as would be recognized by one skilled in the art. Preferably,support surface overlay 100 would have a thickness t of less than twoinches, for example, 1.875 inches, 1.75 inches, 1.625 inches, 1.5inches, 1.375 inches, 1.25 inches, 1.125 inches, 1 inch, 0.875 inch,0.75 inch, 0.625 inch, 0.5 inch, 0.375 inch, 0.25 inch, 0.125 inch orany other thickness less than about 2.0 inches. (Preferably, supportsurface overlay 100 would be designed in a manner allowing for arelatively thin thickness t, for example one inch or less, so thatmotion of a user disposed thereon would be minimized upon inflation anddeflation of inflatable compartments 108, 110.)

Criterion B—Nodal Density

A support surface overlay 100 having at least one inflatable compartmenthaving a nodal contact density, when fully inflated, of at least twocontact node 122 centroids per square decimeter of support surfaceoverlay 100 surface area may provide the Dabir effect. In this context,the term “fully inflated” means inflated to a pressure insufficient tocause plastic deformation of inflatable cells 120 or support surfaceoverlay 100 generally and beyond which an increase in pressure resultsin at most an insignificant effect on the length or width of supportsurface overlay 100 in the area in which the nodal contact density isbeing measured, for example, as illustrated in FIG. 31. Preferably,support surface overlay 100 would have a nodal contact density of fromthree to thirty or more contact nodes per square decimeter. Nodaldensity can be determined by ascertaining the maximum number of contactnodes 122 that can fit within a 10 cm×10 cm area of the surface ofsupport surface overlay 100. For example, nodal density can bedetermined by fitting a mask having a 10 cm×10 cm opening over supportsurface overlay 100 and ascertaining the maximum number of contact node122 centroids that can be made to fit within the opening with supportsurface overlay 100 fully inflated. Nodal density also could bedetermined by fitting a mask having a 10 cm×10 cm opening over atransfer paper removed from contact block 206 at step 316 of the testprocedure described below in connection with Criteria C and D anddetermining the maximum number of contact node 122 centroids as may beascertained from marks imprinted by contact nodes 122 that can be madeto fit within the opening with the transfer paper fully inflated.

Criterion C—Nodal Contact Area Density

A support surface overlay 100 dimensioned so that inflatable cells 120,when inflated to a predetermined internal pressure, are capable ofsupporting a test surface having a predetermined surface area bearing apredetermined load such that less than 75% of the test surface is incontact with contact nodes 122 (and, therefore, at least 25% of the testsurface is not in contact with contact nodes 122) should provide theDabir effect. Preferably, support surface overlay 100 would bedimensioned such that substantially less than 75% is in contact withcontact nodes 122 (and, therefore, substantially more than 25% of thetest surface is not in contact with contact nodes 122) under suchconditions. For example, support surface overlay 100 preferably would bedimensioned such that at least 25%-85% or more of the test surface isnot in contact with contact nodes 122 under such conditions. Thepercentage of contact and non-contact can be determined by any suitablemeans, for example, using pressure mapping equipment or by analysis oftransfer patterns obtained using the test fixture and methodologydescribed below.

Criterion D—Nodal Linear Non-Contact Pattern

A support surface overlay 100 dimensioned so that inflatable cells 120,when inflated to a predetermined internal pressure, are capable ofsupporting a test surface having a predetermined surface area bearing apredetermined load such that at least 25% of the test surfacecorresponding to a line substantially normal to a row of inflatablecells 120 and connecting the centroid of an inflatable cell 120 of suchrow with the centroid of the nearest inflatable cell 120 of another suchrow falling on such line (for example, a line connecting the inflatablecells 120 shown in FIG. 1 as defining the endpoints of the dimension“v”) is not in contact with support surface overlay 100 and less than75% of the test surface corresponding to that line is contact withsupport surface overlay 100. In embodiments wherein inflatable cells 120of neighboring rows are not arranged in columns substantially normal tothe rows, the “v” dimension could be measured as discussed above.

Preferably, support surface overlay 100 would be dimensioned so that asubstantially greater portion of the test surface corresponding to thatline is not in contact with contact nodes 122 under such conditions. Forexample, bladder 100 preferably would be dimensioned such that at least25%-85% or more of the test surface corresponding to that line is not incontact with contact nodes 122 under such conditions. The percentage ofcontact and non-contact can be determined by any suitable means, forexample, using pressure mapping equipment or by analysis of transferpatterns obtained using the test fixture and methodology describedbelow. If using the test fixture and methodology described below, it maybe desirable to obtain and average the foregoing measurements from thecontact patterns associated with three or more pairs of contact nodes.

Percentage of linear contact may be expressed as

% contact=[A+(C−B)+D]/C*100   (Equation 1)

and percentage of linear non-contact may be expressed as

% non-contact=[B−A−D]/C*100   (Equation 2)

where A=the center-to-edge distance of a given contact node 122, B=thedistance between the center of a given contact node and the edge of aneighboring contact node, C=the center-to-center distance betweenneighboring contact nodes, and D=the width of any line of contactbetween horizontally neighboring contact nodes. Dimensions A-D areillustrated in FIG. 32.

Alternatively, % linear non-contact could be determined between any orall pairs of contact nodes 122 that may be connected by a line drawnfrom centroid-to-centroid of such pair(s) of contact nodes withoutpassing through a third contact node 122 or inflatable cell 120. To theextent that this technique might yield different % non-contactmeasurements from pair to pair of contact nodes analyzed, Criterion Dthe analysis should be based on the pair of contact nodes thatdemonstrates the greatest % of linear non-contact at a given testpressure.

2. TEST FIXTURE AND TESTING METHODOLOGY

The test fixture and test procedure described below can be used formaking the foregoing contact and non-contact area determinations atvarious inflatable compartment inflation pressures. With reference toFIGS. 8 and 9, test fixture 200 includes a rigid, flat lower plate 202,a rigid, flat upper plate 204, and a contact block 206 attached to theunderside of upper plate 204. Contact block 206 may be attached to upperplate 204 using any suitable means such that the upper surface of lowerplate 202, lower surface of contact block 206 (the surface of contactblock facing away from upper plate 204) and the upper surface of upperplate 204 are substantially parallel when upper plate 204 is placed uponlower plate 202, as discussed further below. Lower plate may includeguide pins 208 extending upwardly therefrom, and upper plate 204 mayinclude receiving holes 210 configured to receive guide pins 208.

Lower plate 202 and upper plate 204 may be made of any suitable, rigidmaterial, for example, steel. Contact block 206 similarly may be made ofany suitable material, for example, steel or wood. A thin foam layer 212of substantially uniform thickness optionally may be applied to thesurface of contact block facing away from upper plate 204. Foam layer212 may be made of any suitable closed cell foam material, for example,0.125-0.25 inches thick. When used, foam layer 212 should cover theentirety of such surface of contact block 206.

The test procedure 300 is illustrated in flow chart form in FIG. 10.

At step 302, support surface overlay 100 is placed on lower plate 202.Preferably, support surface overlay 100 is loosely stretched intoposition on lower plate 202 so that support surface overlay 100 liessubstantially flatly thereon. Support surface overlay 100 may be securedto lower plate 202, if at all, using any suitable means, for example,positioning bands 214 secured to support surface overlay 100 nearcorners thereof and attached about corners of lower plate 200. Whenused, positioning bands 214 can further serve to loosely stretch supportsurface overlay 100 into position as discussed above.

At step 304, inflatable cells 120 of support surface overlay 100 areinflated to a predetermined pressure.

At step 306, a transfer medium, for example, a layer of paint or ink, isapplied to the upper surface of support surface overlay 100, that is,the surface of support surface overlay 100 facing away from lower plate202.

At step 308, a piece of transfer paper or other material for receivingthe transfer medium applied to support surface overlay 100 is removablyattached to contact block 206 using, for example, tape or another formof removable adhesive, for example, a spray adhesive.

At step 310, upper plate 204 is placed upon support surface overlay 100so that the transfer paper attached to contact block 206 makes contactwith support surface overlay 100. In embodiments wherein lower plate 202includes guide pins 208 and upper plate 204 includes receiving holes210, upper plate 204 is placed upon support surface overlay 100 so thatreceiving holes 210 of upper plate receive guide pins 208 of lower plate202.

At step 312, a predetermined load is gently applied to support surfaceoverlay 100. The predetermined load includes the weight of upper plate204 and contact block 206 and may further include an additional load.Such additional load may include weights or another force applied toupper plate 204 in the direction of support surface overlay 100. Suchadditional load should be applied centrally to upper plate 204 orotherwise in a manner that allows upper plate 204 to evenly apply theload to support surface overlay 100.

At step 314, the load, including upper plate 204, contact block 206, andany additional load, is raised and removed from contact with supportsurface overlay 100.

At step 316, the transfer paper is removed from contact block 206.

At step 318, the foregoing procedure can be repeated at otherpredetermined inflatable compartment inflation pressures. Preferably,the procedure is first conducted using relatively high inflatablecompartment inflation pressures and then successively lower inflatablecompartment inflation pressures but could be conducted in othersequences, as well.

In one embodiment, the surface of contact block 206 that is applied tosupport surface overlay 100 has dimensions of 6″×6″ and contact block206 and upper plate 204 have a combined weight of about 9.4 pounds.Lower plate 202 preferably has dimensions at least somewhat larger thancontact block 206. The transfer paper area is substantially the same asthe area of contact block 206 projected against support surface overlay100. The weight of the transfer paper is negligible. An additional loadhaving a nominal weight of seventy (70) pounds is applied to upper plate204. Inflatable cells 120 are initially inflated to a pressure of 15psi. In successive runs, inflatable cells 120 may be inflated topressures lower than 15 psi in, for example, 1 psi increments.

The data obtained using the foregoing test fixture and methodology canbe analyzed to determine whether and at which operating pressures aparticular support surface overlay 100 is expected to provide Dabireffects.

The details of the foregoing test fixture and test procedure areexemplary and may vary in other embodiments.

3. EXAMPLES

Certain prototype support surface overlays 100, namely, the so-called1.0 and 1.3 support surface overlays, have been used to develop and/orconfirm the foregoing criteria.

The 1.0 support surface overlay is characterized by inflatable cells 120having a nominal diameter of 0.80 inches, nominal horizontal spacing of1.29 inches and nominal vertical spacing of 1.24 inches. The 1.0 supportsurface overly has a nominal thickness t of 0.413 and, therefore,satisfies Criterion A above. The 1.0 support surface overlay has a nodalcontact density of 24 nodes per square decimeter and, therefore,satisfies Criterion B above.

In testing performed using the fixture and methodology set forth above,the 1.0 support surface exhibited the % contact area vs. inflationpressure characteristics shown in Table 1 below.

TABLE 1 Pressure (psi) % Area Contact 1.5 98.75 3.0 63.53 6.0 43.31 9.039.23 12.0 34.87 15.0 30.39

The contact patterns that resulted from the foregoing testing areillustrated in FIG. 11. FIG. 12A is a plot of contact area vs. inflationpressure using the data from Table 1. This data was used to deriveEquation 3 defining % contact area (y) as a function of fill pressure(x):

y=−0.0013x ⁵+0.0675x ⁴−1.3587x ³+13.359x ²−65.401x+171.04   (Equation 3)

at R²=1, where R² is the coefficient of determination. Solving for fillpressure (x) at contact areas of 50%-75% in 5% increments yields fillpressures as a function of contact area as set forth in Table 2. Table 2also sets forth an adjusted pressure as a function of % area contact,the adjusted pressure being 20% lower than the pressure obtained fromEquation 3. The adjusted pressure is intended to adjust for measurementand other errors that may occur during testing.

TABLE 2 % Area Contact Pressure (psi) Adjusted Pressure (psi) 75% 2.371.90 70% 2.62 2.10 65% 2.91 2.33 60% 3.25 2.60 55% 3.69 2.95 50% 4.293.43Based on the above, the 1.0 support surface is expected to provide Dabireffects when operated at adjusted pressures of more than about 1.90 psi.When operated in such a manner, the 1.0 support surface overlay exhibitsa nodal contact area density of less than about 75% area contact and,therefore, satisfies Criterion C above.

Based on the foregoing testing, the 1.0 support surface exhibits the %linear non-contact area vs. inflation pressure characteristics shown inTable 3

TABLE 3 Pressure (psi) % Linear Non-Contact 1.5 0.0 3.0 42.2 6.0 50.89.0 53.7 12.0 58.3 15.0 60.0The contact patterns that resulted from the foregoing testing areillustrated in FIG. 11. FIG. 12B is a plot of linear non-contact vs.inflation pressure using the data from Table 3. This data was used toderive Equation 4 defining % linear non-contact (y) as a function offill pressure (x):

y=0.0042x ⁵−0.1954x ⁴+3.447x ³−28.623x ²+111.88x−114.09   (Equation 4)

at R²=1. Solving for fill pressure (x) at linear non-contact values of25%-50% in 5% increments yields fill pressures as a function of linearnon-contact as set forth in Table 4. Table 4 also sets forth an adjustedpressure as a function of % linear non-contact, the adjusted pressurebeing 20% lower than the pressure obtained from Equation 4. The adjustedpressure is intended to adjust for measurement and other errors that mayoccur during testing.

TABLE 4 % Linear Non-Contact Pressure (psi) Adjusted Pressure (psi) 25%2.17 1.74 30% 2.36 1.89 35% 2.58 2.06 40% 2.85 2.28 45% 3.23 2.58 50%3.91 3.13Based on the above, the 1.0 support surface overlay is expected toprovide Dabir effects when operated at adjusted pressures of at least1.74 psi. When operated in such a manner, the 1.0 support surfaceoverlay exhibits a nodal linear non-contact pattern of 25% or morenon-contact and, therefore, satisfies Criterion D above.

The 1.3 support surface overlay is substantially identical to the 1.0support surface overlay but is dimensionally larger by a nominal factorof 1.3. The 1.3 support surface overlay is characterized by inflatablecells 120 having a nominal diameter of 1.06 inches, nominal horizontalspacing of 1.69 inches and nominal vertical spacing of 1.59 inches, athickness of 0.661 inches a nodal contact density of 15 nodes per squaredecimeter. As such, the 1.3 support surface overlay satisfies Criteria Aand B above. The 1.3 bladder is expected to satisfy Criteria C and D, aswell.

Other examples could be made having other dimensions and satisfying oneor more of Criteria A-D. Similar testing and methodology could be usedto determine whether a bladder 100 having any dimensions would provideDabir effects.

4. CONTROL SYSTEMS

As shown in FIG. 13, support surface overlay 100 can be included in asystem 400 further including a pneumatic control system (PCS) 402configured to control the inflation and deflation of first and secondinflatable compartments 108, 110. (PCS 402 is illustrated as includingoptional means for controlling a third inflatable compartment.) PCS 402may include a pneumatic pump 406, a plurality of regulator valves 408,and a plurality of dump valves 410 in fluid communication with fluidconduits 124, 126 of first and second inflatable compartments 108, 110via pneumatic lines 420. Pneumatic lines 420 may be connected to PCS 402and/or inflatable compartments 108, 110 of support surface overlay 100via quick disconnect fittings 422 or by other suitable means.

Pump 406 may be embodied as any form of pump suitable for inflatinginflatable compartments 108, 110 as discussed herein. For example, pump406 could be embodied as a scroll pump having PWM drive control allowingfor duty cycle control sufficient to enable direct inflation ofinflatable compartments 108, 110 without the need for an accumulator. Insome embodiments, PCS 402 could be supplied with air from an externalsource, for example, a hospital's high pressure air system. In suchembodiments, pump 406 could be bypassed or omitted.

Regulator valves 408 provide a means to charge inflatable compartments108, 110 with fluid. Dump valves 410 provide a means for allowing all ofinflatable compartments 108, 110 to be rapidly deflated upon demand, forexample, in the event of a need to perform CPR on a patient lying on thedevice (CPR might not be effectively performed upon a patient lying onthe device with one or more of inflatable compartments 108, 110inflated). Dump valves 410 could be omitted if desired, particularly inembodiments in which regulator valves 408 provide sufficient reverseflow capacity. A separate and independently controlled regulator valve408 and dump valve 410 may be provided for each of first inflatablecompartment 108 and second inflatable compartment 110. In someembodiments, however, a single regulator valve 408 and dump valve 410could control inflation and deflation of both first inflatablecompartment 108 and second inflatable compartment 110.

PCS 402 may also include an accumulator 414, an exhaust muffler 416,and/or a safety kill switch 418. Accumulator 414 could be provided tostore pressurized air for operation of bladder 100, and exhaust muffler416 could be provided to silence air as it escapes bladder 100. Anintake muffler and replaceable intake filter are not shown but alsocould be provided to silence and filter air being drawn into pump 406.Safety kill switch 418 could be provided to shut off power to PCS 402,as may be desired by an operator.

In some embodiments (not shown), PCS 402 could be configured to providepneumatic control for more than one bladder 100. For example, a singleregulator valve 408 and single dump valve 410 could be in fluidcommunication with the first inflatable compartment 108 and/or secondinflatable compartment 110 of two or more support surface overlays 100.Alternatively, PCS 402 could include a first pneumatic pump 406 andfirst set of regulator and dump valves 408, 410 for a first supportsurface overlay 100 and an additional pneumatic pump 406 and additionalsets of regulator and dump valves 408, 410 for each additional supportsurface overlay 100.

PCS 402 or any portion thereof may be provided in a portable case sothat these components may be easily transported as a unit.

PCS 402 may include an electronic control unit (ECU) 404 that controlspump 406 and valves 408, 410, thereby controlling the inflation anddeflation of inflatable compartments 108, 110. ECU 404 may bepre-programmed to selectively inflate and deflate first and/or secondinflatable compartments 108, 110 according to any number and variety ofpatterns and/or cycles. Also, ECU 404 may include a user interfaceconsole (UIC) 428 having a user interface panel 430 through which a usercan select any particular inflation/deflation pattern or cycle into ECU404 and/or otherwise control the operation of ECU 404. In otherembodiments, ECU 404 could enable a user to create custominflation/deflation patterns or cycles or manually control PCS 402. UIC428 could be tethered to ECU 404 or it could control ECU 404 wirelessly.

With reference to FIG. 14, user interface panel 430 may include anon/off switch 432, a plurality of profile switches 434, and an emergencyoff switch 436. On/off switch 432 allows a user to toggle PCS 402 on andoff. Each of profile switches 434 is associated with a particular,predefined pattern and cycle of inflation, dwell, and deflation of firstand second inflatable compartments 108, 110. The pattern and cycle ofinflation/dwell/deflation associated with each profile switch 434 can,for example, be started by selecting that profile switch 434 a firsttime and stopped by selecting that profile switch 434 a second time. Theemergency stop switch 436 can be used to, for example, turn off pump 406and rapidly deflate support surface overlay 100 in the case of anemergency, for example, in the event CPR needs to be used on a personlying on support surface overlay 100. Each of the foregoing switches caninclude visual, audible, and vibratory haptic feedback mechanisms toassist the user in confirming which switches and/or modes of operationof PCS 402 have been selected.

A block diagram illustrating an example of the functions (for example,exemplary inflation/deflation times and patterns for “Profile 1”,“Profile 2”, and “Profile 3”) associated with each of those switches isprovided in FIG. 15.

FIGS. 16-21 illustrate examples of various predefined patterns andcycles of inflation, dwell and deflation of first and secondcompartments 108, 110. As FIG. 16 illustrates, inflatable compartments108, 110 could be inflated when one of switches 434 is selected. Thisinitial inflation may take a predetermined amount of time, for example,about 15 seconds. After an optional, predetermined dwell time, forexample, 15 seconds, one of the patterns and cycles can begin. As FIG.17 illustrates, both of inflatable compartments 108, 110 can be deflatedafter a pattern and cycle of inflation/deflation is complete, which alsocan take about 15 seconds—unless the pattern and cycle is stopped wheninflatable compartments 108, 110 are not fully inflated, in which caseit will take less than 15 seconds. As FIG. 18 illustrates, both ofinflatable compartments 108, 110 can be deflated in 5 seconds or less ifthe emergency off switch 436 is actuated.

FIG. 19 illustrates the pattern and cycle associated with first profileswitch 434 (“Profile 1”); FIG. 20 illustrates the pattern and cycleassociated with second profile switch 434 (“Profile 2”); and FIG. 21illustrates the pattern and cycle associated with third profile switch434 (“Profile 3”). Although each of those figures illustrates linearinflation and deflation rates, such linearity is not required.

Although the user interface is described above as only having threedifferent, predefined patterns and cycles of inflation/deflation, it canprovide functionality by which a user can define and store otherpatterns and cycles of inflation/deflation and assume full manualcontrol over the inflation and deflation of first and second inflatablecompartments 108, 110. UIC 428 provides the main point of input from thedoctor, nurse, or patient and controls the patterns and cycles ofinflation/deflation by controlling solenoids that open and closeregulator valves 408 and dump valves 410. It also can control pressureregulators that determine and control inflation pressures in first andsecond inflatable compartments 108, 110 and operation of pneumatic pump406. ECU 404 can also be programmed to monitor, control, and collectdata from sensors that examine load, pressure, temperature, andmoisture, with or without respect to time.

The operation of ECU 404 and PCS 402 preferably are implemented using asuitable computing processor or processing platform that is capable ofperforming the functions and operations in accordance with theinvention. Each of those devices may include a user interface and/ordisplay for operating the computing processor or processing platform.All or parts of the system and processes can be stored on or read from amemory or computer readable media.

PCS 402, ECU 404, and pneumatic pump 406, and valves 408, 410 may bebattery powered (VDC) or wall outlet powered (VAC). System 400preferably operates at a noise level lower than 40 dB and can cycle a400 pound load at least 10,000-25,000 times. Preferably, the maximumcontinuous current draw of each component is 5 amps.

In certain embodiments, PCS 402 could be replaced or supplemented withan analogous system configured to inflate and deflate inflatablecompartments 108, 110 using another gas or a liquid instead of air, aswould be understood by one skilled in the art.

The control system could be set up to synchronize the inflation and/ordeflation of inflatable compartments 108, 110 to natural body orenvironmental rhythms, for example, heartbeat, pulse, respiration rate.Doing so could have a beneficial psychological or therapeutic effect.The control system also could include means for effecting active noisecancellation to further muffle sounds made by system 400.

Support surface overlay 100 may be provided with means, for example, aone-time programmable (OTP) chip including the support surface's serialnumber, for self-identification when connected to a control system, aswell as means, for example, an erasable programmable memory (EPROM) forstoring other information relevant to the bladder, for example, thenumber of inflation/deflation cycles it has been subjected to. Thecontrol system could be configured to not operate a bladder if thecontrol system does not recognize the bladder's serial number or if itdetermines that the bladder has been used for an excessive number ofcycles.

The control system also could be adapted to interface with a computernetwork to allow remote indication of the operation and status of thesystem, including any faults or alarms. For example, the control systemcould output alarms indicative of the need for filter replacement orother maintenance, the number of inflation/deflation cycles supportsurface overlay 100 has been subjected to, attempts to connect to thecontrol system a support surface overlay 100 having a serial number notrecognized by the system, and the like.

5. ANTI-SHEAR PROVISIONS

Support surface overlay 100 may have a propensity to contract from sideto side and/or end to end when either or both of first inflatablecompartment 108 and second inflatable compartment 110 are inflated, aswould be recognized by one skilled in the art. Such contraction maycause shearing or tearing of tissue of a user disposed on supportsurface overlay 100, as would be understood by one skilled in the art.

The foregoing contraction/shearing effect may be mitigated by providingsupport surface overlay 100 with optional relief cuts 136 perforatingupper sheet 102 and lower sheet 104 of support surface overlay 100between adjacent inflatable rows 114, 118 of first and second inflatablecompartments 108, 110, for example, as shown in FIG. 6. Relief cuts 136can be formed in support surface overlay 100, for example, within theconfines of seams 106 or elsewhere without penetrating the pressureboundaries of first inflatable compartment 108 or second inflatablecompartment 110. Relief cuts 136 can be formed by any suitable means,for example, by die, knife or laser cutting. A circular stress relief138 can be provided at each end of each relief cut.

Relief cuts 136 allow displacement of certain portions of supportsurface overlay 100 in response to inflation of first inflatablecompartment 108 and/or second inflatable compartment 110 whilemitigating side-to-side and/or end to end contraction of support surfaceoverlay 100 and corresponding displacement of inflatable cells 120 andcontact nodes 122 while under load. In the FIG. 6 embodiment, reliefcuts 136 are elongated and provided in a so-called 3-1 pattern, whereina relief cut 136 is provided over 5π radians of every 6π radians ofsinusoidally-shaped seams 106 defining an inflatable row 114, 118 of aninflatable compartment 108, 110. In this embodiment, every third“trough” of each seam 106 defining an inflatable row 114, 118 of aninflatable compartment 108, 110 lacks a relief cut 136. These uncutregions 140 form an X-pattern, as shown in FIG. 6.

In other embodiments, support surface overlay 100 could be provided withmore or fewer relief cuts 136 than shown in FIG. 6 and/or in differentpatterns than shown in FIG. 6. For example, relief cuts 136 could extendover as few as π radians of every 2π radians or less, or over the fullextent of rows 114, 118 from manifold 112 to manifold 116. In supportsurface overlays 100 not having sinuous seams 106, relief cuts 136 couldbe provided between rows of inflatable compartments in a similar manner,as would be understood by one skilled in the art.

Relief cuts 136 can be, but need not be, provided throughoutsubstantially the entirety of support surface overlay 100 or a lesserportion of support surface overlay 100. The pattern of relief cuts 136shown in FIG. 6, when provided throughout substantially the entirety ofsupport surface overlay 100, may substantially mitigate side-to-sideand/or end-to-end contraction of support surface overlay 100 uponinflation of first inflatable compartment 108 and/or second inflatablecompartment 110 while supporting a user.

The foregoing contraction/shearing effect also may be mitigated by meansof an anti-shear liner (for example, liner bag 500 as shown in FIG. 24)loosely fit over or around support surface overlay 100. Such a liner maybe made of a single layer of material sufficiently slippery to notsecurely adhere to either or both of support surface overlay 100 and auser disposed thereon under shearing loads that might be produced wheninflatable compartments 108, 110 of support surface overlay 100 areinflated and deflated. Alternatively, such a liner may be made of twolayers of material, for example, rip-stop nylon, sufficiently slipperyto not securely adhere to each other under shearing loads that might beproduced when inflatable compartments 108, 110 of support surfaceoverlay 100 are inflated and deflated. Anti-shear liners, when provided,preferably would be readily removable from support surface overlay 100and machine washable or otherwise readily cleanable.

In another embodiment, shown in FIGS. 27A and 27B, support surfaceoverlay 100 could be contained within substantially fluid-tight envelope164 made, for example, of an upper sheet 160 and a lower sheet 162joined together in a substantially fluid-tight manner, for example, by aperimeter seal 170 (which could be an RF weldment). Envelope 164 couldinclude sealing grommets 166 for receiving fluid conduits 124, 126 in agenerally fluid-tight manner.

Envelope 164 could be attached to corners of support surface overlay 100by RF spot welds 168 or otherwise. Alternatively, support surfaceoverlay 100 could “float” within envelope 164. Additional spot welds 148could be provided to prevent undue ballooning of envelope 164 whenpressurized. Relief cuts 136 could be provided in support surfaceoverlay 100 proximate the corners thereof. The interior region ofenvelope 164 could be filled with a lubricating fluid 172 or othersubstance enabling support surface overlay 100 to expand and contactwithin envelope 164 without imparting substantial shear forces on a userdisposed thereon.

In another embodiment, a support surface overlay 100 including or notincluding relief cuts 136 could be encapsulated in a self-skinned foamliner. In such an embodiment, the foam liner could absorb or otherwisemitigate shearing effects, provide comfort and be easily cleanable.

6. MICROCLIMATE CONTROL

Support surface overlay 100 can further be configured to allow forcontrol of the microclimate about a user disposed on support surfaceoverlay 100 by incorporating a ventilation and air conditioning systemthat discharges air or another medium into the region about the upperside of support surface overlay 100. For example, upper sheet 102 ofsupport surface overlay 100 could be made of a material sufficientlypermeable to enable controlled release of air therefrom to provideclimate control, yet sufficiently fluid-tight to allow for inflation ofinflatable compartments 108, 110 as discussed above. In such anembodiment, a suitable sealant (not shown) could be applied to selectedportions of upper sheet 102. The sealant would preclude fluid fromflowing through portions of upper sheet 102 to which the sealant hadbeen applied. This technique can be used to effect better distributionof fluid flow through upper sheet 102. Alternatively, upper sheet 102could be perforated with small holes (not shown) at predeterminedlocations in order to provide a controlled release of air. The releasedair can be channeled through the interstitial regions defined byinflatable cells 120, contact nodes 122 and a user lying thereon.

In another embodiment, as shown in FIGS. 25A-25D, a third sheet 142could be attached to the lower side of support surface overlay 100 suchthat third sheet 142 and support surface overlay 100 form a plenum 144there between. For example, third sheet 142 could be RF welded to aperipheral portion of lower sheet 104 or another portion of supportsurface overlay 100 by means of perimeter weld 146 to form plenum 144.Third sheet 142 also could be attached to portions of support surfaceoverlay 100 within the peripheral portion thereof by means of one ormore spot welds 148 or otherwise in order to prevent ballooning ofplenum 144 when the plenum is pressurized, as discussed below.Preferably, third sheet 142 is substantially impermeable andsufficiently flexible to not adversely affect inflation and deflation ofinflatable compartments 108, 110. Third sheet 142 could be made of thesame material used to make first and second sheets 102, 104.

An air inlet tube 150 could be provided in fluid communication with thisplenum to allow introduction of air or another medium to the plenum.Support surface overlay 100 could include perforations, for example, atpredetermined locations in seams 106 through which this air could escapeand provide ventilation to a user lying on a support surface overlay100. Such perforations could be embodied as relief cuts 136. Inembodiments not including relief cuts 136, such perforations could takeother forms, for example, ventilation ports 152. Some embodiments couldinclude relief cuts 136 and ventilation parts 152. As set forth above,the released air can be channeled through the interstitial regionsdefined by inflatable cells 120, contact nodes 122 and a user lyingthereon.

An optional fourth sheet 154 as shown in FIGS. 25B-25C (optional fourthsheet 154 is not shown in FIGS. 25A and 25D for clarity) may be attachedto the upper side of support surface overlay 100. Fourth sheet 154preferably would be made of a material, for example, nonwoven TPUfabric, sufficiently permeable to allow ventilating air escaping fromthe plenum to pass there through and into the interface region betweensupport surface overlay 100 and a user disposed thereon. Fourth sheet154 could be made of a material that also provides anti-shearcharacteristics, as discussed above.

Supply air for plenum 144 could be provided from various sources. Forexample, the exhaust from inflatable compartments 108, 110 could bedischarged into plenum 144 and thereby be used as ventilating air. PCS402 could be modified to include additional valving and control logic toenable such a flow path. Alternatively, supply air for plenum 144 couldbe provided separately, either from pump 406 or another source (notshown).

The air supplied to plenum 144 could be heated cooled, humidified,dehumidified, or otherwise conditioned to enhance the health and/orcomfort of a user disposed on support surface overlay 100. Also, drugs,antiseptics or other media could be added to the air supplied to plenum144 for delivery to the region about the upper side of support surfaceoverlay 100.

A heating element could be provided behind support surface overlay 100to provide additional heating. A carbon fiber heating element could beused to maintain x-ray translucency.

7. PERIPHERAL SUPPORT ELEMENTS AND ENCLOSURES

System 400 may also include a double thickness liner bag 500 (see FIG.22), a foam mat (not shown), a head rest 522 (see FIG. 23), inflatableside bladders 524 (see FIG. 32), and a dynamic edge rail 526 (see FIG.32). Liner bag 500 can substantially envelop support surface overlay100, the foam mat, head rest 522, inflatable side bladders 524, anddynamic edge rail 526, thereby forming pad 520. Liner bag 500 mayenclose the foregoing components using a medical grade ziploc or zippersystem (not shown) that allows for easy disassembly of top and bottomportions for quick maintenance and/or replacement.

Liner bag 500 can assist in providing patient comfort and protecting pad520, while allowing substantially uninhibited operation of inflatablecompartments 108, 110 of support surface overlay 100. Liner bag 500 maybe designed to allow for slip between layers that provide low frictionacross its surfaces as well as elasticity so as to not impair theperformance of support surface overlay 100. Also, liner bag 500 maystretch in a manner that allows for a user's weight to be supported bycontact nodes 122 without bag 500 being ripped or torn or causing ahammock effect. Liner bag 500 may also be impervious to various fluidsso as to protect pad 520 from foreign matter, such as urine, feces,blood, and alcohol. Liner bag 500 preferably can be easily removed andcleaned and/or be cleaned without being removed using inflatable sidebladders 524 to pull the surface of liner bag 500 taut. In someembodiments, liner bag 500 could be made of or treated with ananti-bacterial/anti-microbial material. (Similarly, support surfaceoverlay 100 could itself be treated with ananti-bacterial/anti-microbial material.)

Liner bag 500 may include one or more of: sealing grommets 502 thatallow pneumatic lines 420 to be connected between inflatablecompartments 108, 110 and pneumatic pump 406; a bottom layer 504 andstraps (not shown) that hold liner bag 500 and its contents securely toa table, bed, or medical imaging device on which it may be used; aninner protective layer 506 for protecting pad 520 within liner bag 500and protecting liner bag 500 from ripping or tearing; and a stretchableouter layer 508 that stretches as contact nodes 122 press against linerbag 500. Bottom layer 504 preferably is made of a fabric, for example,the SLIP-NOT brand fabric made by Eastex Products, Inc., that holds upstrongly to wear and abrasion and also offers grip and non-skidperformance under both wet and dry conditions. Inner protective layer506 preferably is made of a nylon-reinforced rip-stop material.Stretchable outer layer 508 preferably is made of a fluid-proof andstain-resistant fabric, for example, the TEK STRETCH 2 brand fabric madeby Eastex Products, Inc., that stretches in the two directionsperpendicular to the plane of the fabric. The straps (not shown)preferably are made of nylon and preferably can support a 200 poundretention load. Liner bag 500 may also include an inner slip/shearreducer 510 disposed between non-slip bottom layer 504 and innerprotective layer 506 to reduce slip/shear between those layers.

FIGS. 23A, 23B and 24 illustrate an example of a pad 520 that can beenclosed in liner bag 500. In the exemplary embodiment of pad 520illustrated in FIG. 23A, a plurality of support surface overlays 100 areassembled in the shape of a catheter table, except for head rest 522,which is formed from a durable soft material. Pad 520 also includesinflatable side bladders 524 disposed along the sides of support surfaceoverlay 100. Inflatable compartments 108, 110 are illustratedschematically in block form but in practice would take a form asdiscussed above in the detailed description of support surface overlay100. Inflatable side bladders 524 can be positioned substantiallyperpendicular to the alternating rows of inflatable compartments 108,110. Preferably, inflatable side bladders 524 are thicker when inflatedthan inflatable compartments 108, 110. For example, inflatable sidebladders 524 can be approximately 1½ inches wide and 1½ inches thick.The catheter table, not including head rest 522, can be approximately100 inches long, approximately 24 inches wide at its widest point, andapproximately 14 inches wide at its narrowest point. In an exemplaryembodiment as illustrated in FIG. 23, inflatable compartments 108, 110each have a volume of approximately 875 in³, and inflatable sidebladders 524 have a volume of approximately 450 in³. Dimensioned assuch, inflatable side bladders 524 can be inflated and deflated in aboutthe same amount of time as each of first and second inflatablecompartments 108, 110 (e.g., 15 seconds) at about half the flow rate(for example, about 2.0 CFM versus about 1.0 CFM). Other configurations,other dimensions, and other flow rates may be implemented as desired tosuit other applications and to fit different tables, beds, and medicalimaging devices. The dimensions and volumes of inflatable compartments108, 110 and inflatable side bladders 524 may also be different based onthe application and the desired performance, such as the flow raterequired to fill them.

Inflatable side bladders 524 can be inflated in a cleaning mode tofacilitate cleaning of liner bag 500. The cleaning mode stretches linerbag 500 to remove any wrinkles or folds therefrom so that the entireexternal surface of the liner bag 500 can be more easily wiped orotherwise cleaned. Side bladders 524 also can incorporate a secondarychamber to provide a dynamic edge rail 526. Dynamic edge rail 526comprises a further inflatable zone that can be inflated or deflated asdesired, for example, to provide side bolstering for a patient. In thealternative, the dynamic edge rail 526 can be formed from a durable softmaterial that is attached or to otherwise positioned at the sides ofsupport surface overlay 100.

As an alternative to forming support surface overlays 100 in the shapeof the load-bearing device on which they will be used, support surfaceoverlays 100 can be made in a standard, modular configuration anddisposed on a foam insert 530 that is formed in the shape of theload-bearing redistribution device on which support surface overlay 100is to be used. Thus, instead of providing support surface overlays 100in several shapes and sizes to conform to the shape of different loadbearing devices, foam insert 530 can be formed to the shape of differentload-bearing devices providing the base support for support surfaceoverlay 100. Modifying the shape of foam insert 530 for each differentload-bearing device may be easier and less costly than modifying supportsurface overlays 100 for specific applications. Foam insert 530preferably is made of a medium density medical grade cellular urethanefoam, such as the PORON brand foam made by Stockwell Elastomerics, Inc.Different and/or additional materials may also be used to constructliner bag 500 depending on the application and the desired attributes ofliner bag 500.

As illustrated in FIG. 24, foam insert 530 can be formed with recessedportions 532 that are configured to receive one or more modular supportsurface overlays 100 therein. Also, head rest 522 may be formed with arecessed portion 534 configured to receive different patient headsupport inserts 536 therein. Recessed portions 532 and 534 can act asnestable pockets that hold support surface overlays 100 and headsupports 536 in place on the load-bearing device on which they are beingused. Support surface overlays 100 can be used with different foaminserts 530 to conform to different load-bearing devices without theneed to make countless different sizes and configurations of supportsurface overlays 100 for each different load-bearing device on whichthey will be used. Also, patient head supports 526 can be of differentshapes and sizes to support heads of different sizes and shape and toprovide different types of support.

8. ENVIRONMENTAL SENSING

Capacitive, field effect, or other types of sensors could beincorporated into or attached to, for example, the upper and/or lowerside of support surface overlay 100 to sense the presence of water,urine, feces, blood, or other contaminants that might be introduced tosupport surface overlay 100 during use. Alternatively, such sensorscould be incorporated or attached to a layer attached to the undersideof support surface overlay, for example, as described above inconnection with the microclimate and/or anti-shear enhancements. Similarsensors could be incorporated into or attached to, for example, theupper and/or lower side of support surface overlay 100 to detect abottom out condition wherein the load (for example, a user) disposed onsupport surface overlay 100 causes at least a portion of support surfaceoverlay 100 to flatten out such that the load is supported directly bythe underlying support surface instead of by contact nodes 122 ofsupport surface overlay 100. FIG. 25E illustrates a sensor 180incorporated into or disposed in third sheet 142 such that sensor 180could be used to detect liquid or moisture intrusion into plenum 144 ora bottoming out condition. Also, thermocouples or other temperaturesensing means could be provided to monitor the temperature about supportsurface overlay 100 and the region in which it interfaces with a userdispose thereon.

Such sensors could be electrically coupled to a monitoring system viaelectrical traces embedded within support surface overlay 100 or affixedto a surface thereof. Such a monitoring system could be incorporatedinto the ECU 404 of PCS 402 or otherwise into UIC 428 or it could beindependent of same. Quick disconnect electrical connectors could beprovided to facilitate electrical connections between support surfaceoverlay 100 and the monitoring or control system.

9. PRESSURE MAPPING

Support surface overlay 100 could be used in connection with pressuremapping technology in order to provide a user with information directedto the interface between support surface overlay 100 and a user lyingthereon. For example, a pressure sensing mat (not shown) could be placedbetween support surface overlay 100 and an underlying bed, mat, mattressor other structure. The pressure sensing mat could provide outputindicative of the interface pressure between support surface overlay 100and a user at various points of contact by means of pressure transferredthrough support surface overlay 100 to the mat. Such a mapping systemcould be used to determine optimal inflation pressures for inflatablecompartments 108, 110 and/or to detect a bottom out condition wherein auser disposed on support surface overlay 100 is overloading supportsurface overlay 100 such that the user is being supported by theunderlayment under support surface overlay 100 instead of by contactnodes 122.

10. USE AS SKIN PUMP

Support surface overlay 100 could be adapted for direct attachment byadhesive or other means to a user's body. Such direct attachmenttechniques could help maintain desired alignment and positioning supportsurface overlay 100 with respect to the user's body. To the extent notmitigated by the inclusion of relief cuts 136, operation of supportsurface overlay 100 when adhered directly to a user's body could have apumping effect that might promote intersticial and other blood flow inthe affected area of the user's body.

In other applications, support surface overlay 100 could be incorporatedinto a cast or support stocking to promote blood flow in the tissue of awearer thereof.

11. PROSTHETIC INTERFACE

FIG. 28 illustrates a support surface overlay 100 disposed within theresidual-limb receiving cup 600 of a prosthetic leg and adapted toreceive residual limb 602. In this embodiment, support surface overlay100 may include one or more inflatable compartments. Cup 600 may includea port 604 through which one or more fluid conduits 626, 628corresponding to the one or more inflatable compartments may pass. Fluidconduits 626, 628 may be connected to a fluid pump or cylinder, forexample, as discussed below.

FIG. 29 shows a embodiment of a prosthetic foot 606 including a firstbladder 608 located in the fore-region thereof and a second fluid-filledbladder 610 located in the heel region thereof. First and secondbladders 608, 610 could be in fluid communication with correspondinginflatable compartments of one or more support surface overlays 100disposed with limb-receiving cup 600. First bladder 608 tends to becomecompressed in response to a pressure applied to the fore-region ofprosthetic foot 606 and de-compressed in response to removal of pressurethereto, as might occur during a normal walking activity. Similarly,second bladder 610 tends to become compressed in response to pressureapplied to the heel region of prosthetic foot 606 and de-compressed inresponse to removal of pressure thereto.

First and second bladders 608, 610 could be in fluid communication withfirst and second inflatable compartments 108, 110, respectively, ofsupport surface overlay 100 in cup 600 via fluid conduits 626, 628. Thesystem defined thereby could be filled with a suitable fluid, forexample, a silicone hydraulic fluid. As such, bladders 608, 610 couldalternately pressurize and de-pressurize inflatable cells of inflatablecompartments of support surface overlay(s) 100 in response to walkingactivity of a user wearing the apparatus.

FIG. 30 shows another embodiment of a prosthetic foot 606 includingfirst, second and third articulating elements 612, 614, 616 connected bypivot points 618, 620. A first fluid cylinder 622 is disposed betweenfirst and second articulating elements 612, 614 such that first fluidcylinder 622 and the fluid therein is alternately compressed anddecompressed in response to articulation of first articulating element612 with respect to second articulating element 614 as might occurduring normal walking activity. Similarly, a second fluid cylinder 624is disposed between second and third articulating elements 614, 616 suchthat second fluid cylinder 624 is alternately compressed anddecompressed in response to articulation of second articulating element614 with respect to third articulating element 616.

First and second fluid cylinders 622, 624 could be in fluidcommunication with first and second inflatable compartments 108, 110,respectively, of support surface overlay 100 in cup 600 via fluidconduits 626, 628. The system defined thereby could be filled with asuitable fluid, for example, a silicone hydraulic fluid. As such,fluid-filled bladders 608, 610 could alternately pressurize andde-pressurize inflatable cells of inflatable compartments of supportsurface overlay(s) 100 in response to walking activity of a user wearingthe apparatus.

12. OPERATING INSTRUCTIONS

Support surface overlay 100 may be provided with operating instructionsinstructing a user to operate support surface overlay 100 in a mannerthat provides the Dabir effect. The instructions may be provided in apackage including one or support surface overlays 100. Alternatively,such instructions may be provided separately in hard copy or, forexample, electronically on a compact disc or through an Internetwebsite.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A support surface overlay comprising: a first flexible sheet and asecond flexible sheet; said first flexible sheet joined to said secondflexible sheet at predetermined locations in a substantially fluid-tightmanner, thereby defining a plurality of spaced-apart, selectivelyinflatable cells and a fluid channel connecting at least one of saidinflatable cells with one other of said inflatable cells; said firstflexible sheet and said second flexible sheet being substantiallycontinuous at locations where said first flexible sheet is joined tosaid second flexible sheet; and said inflatable cells having a nominalmaximum thickness, when inflated, of about two inches.
 2. A supportsurface overlay comprising: a first flexible sheet and a second flexiblesheet; said first flexible sheet joined to said second flexible sheet atpredetermined locations in a substantially fluid-tight manner, therebydefining a plurality of spaced-apart, selectively inflatable cells and afluid channel connecting at least one of said inflatable cells with oneother of said inflatable cells; said inflatable cells and fluid channelsoperable at inflation pressures of at least about six psi.
 3. A supportsurface overlay comprising: a first flexible sheet and a second flexiblesheet; said first flexible sheet joined to said second flexible sheet atpredetermined locations in a substantially fluid-tight manner, therebydefining a plurality of spaced-apart, selectively inflatable cells and afluid channel connecting at least one of said inflatable cells with oneother of said inflatable cells; said inflatable cells, when inflated,defining corresponding outwardly extending contact nodes having a nodalcontact density of at least two contact nodes per square decimeter.
 4. Asupport surface overlay comprising: a first flexible sheet and a secondflexible sheet; said first flexible sheet joined to said second flexiblesheet at predetermined locations in a substantially fluid-tight manner,thereby defining a plurality of spaced-apart, selectively inflatablecells and a fluid channel connecting at least one of said inflatablecells with one other of said inflatable cells; said inflatable cellsbeing dimensioned and spaced such that said support surface overlay iscapable of supporting a test surface applying a pressure of at least twopounds per square inch thereto such that no more than 75% of said testsurface is in contact with said support surface overlay.
 5. A supportsurface overlay comprising: a first flexible sheet and a second flexiblesheet; said first flexible sheet joined to said second flexible sheet atpredetermined locations in a substantially fluid-tight manner, therebydefining a plurality of spaced-apart, selectively inflatable cells and afluid channel connecting at least one of said inflatable cells with oneother of said inflatable cells; said inflatable cells being dimensionedand spaced such that said support surface overlay is capable ofsupporting a test surface applying a pressure of at least two pounds persquare inch thereto such that said test surface is in linear contactwith said support surface overlay along no more than 75% of a line drawnbetween the respective centroids of a pair of neighboring ones of saidinflatable cells in one of said columns.
 6. A method of operating asupport surface for an individual, comprising the steps of: providing asupport having a a first flexible sheet and a second flexible sheet,said first flexible sheet joined to said second flexible sheet atpredetermined locations in a substantially fluid-tight manner, therebydefining a plurality of spaced-apart, selectively inflatable cells and afluid channel connecting at least one of said inflatable cells with oneother of said inflatable cells; and selectively inflating saidinflatable cells to a pressure of at least six psi.